1. Field of the Invention
The present invention relates to an image forming system, an image forming apparatus, and a method of recovering the image forming system from an energy saving mode.
2. Description of the Related Art
In image forming systems including external controllers that receive a printing request from client terminals and image forming apparatuses that are connected to the external controllers via a network and perform printing and reading of images based on the printing request from the external controllers, it is required to reduce power consumption and realize quick start up. Specifically, it is preferable that the external controllers enter in an energy saving mode in conjunction with power OFF of the image forming apparatuses and recover from the energy saving mode in conjunction with power ON of the image forming apparatuses.
However, if the image forming apparatuses and the external controllers are connected to each other via Ethernet (registered trademark) and when power supply to Ethernet circuits is suspended because the external controller enters in the energy saving mode, Ethernet functions are not effective. Therefore, it is difficult to recover the external controller from the energy saving mode in conjunction with power ON of the image forming apparatus.
A conventional technology for solving the above problems is disclosed in, for example, Japanese Patent Application Laid-open No. 2003-162398. In the conventional technology, a spread spectrum communication circuit of a power-supply-unit control circuit in a printer control circuit conducts data communication with an information processing apparatus via a distribution line. A power supply control unit controls a start and a stop of supply of power from a power supply circuit to a printer controller or a printer engine depending on attribute of communicated data. As a result, wiring of communication lines or control lines can be simple and extra connection lines are not needed. Furthermore, power consumption can be reduced to the same level as that attained in a standby mode in which image forming operation is suspended and supply of power is suspended.
However, in the conventional technologies, energy saving control is performed only when power is being supplied to both the information processing apparatus and the image forming apparatus. Therefore, if the image forming apparatus is powered OFF, the energy saving control cannot be performed.